1. Field of the Invention
The present invention relates to a conveying pipe for hydraulically transporting solids, such as sand, gravel or also concrete.
2. Description of the Related Art
Conveying pipes of the above-described type are subjected to significant internal wear because of the abrasive solids. Consequently, the pipes must be replaced relatively frequently. The intensity of the wear depends on the position of each conveying pipe in the entire pipeline and the intensity of the wear is dependent on whether it is a straight pipe or a curved pipe. To ensure that each conveying pipe can be removed transversely out of the pipeline and can also be inserted again transversely into the pipeline, each conveying pipe is composed of a straight or curved pipe portion and of coupling flanges at the ends of the pipe portion, wherein the coupling flanges protrude radially above the outer surface of the pipe portion. The outer end faces of the coupling flanges which face away from each other are each located in the transverse planes of the end faces of the conveying pipe.
The fluid-tight connection of two successive conveying pipes is effected by coupling rings composed of two shells which are placed around the coupling flanges and are clamped. Sealing elements can additionally be embedded in the inner sides of the coupling rings. In order to make the conveying pipes of different manufacturers exchangeable, an international agreement provides that the total width of two coupling flanges to be connected to each other including a coupling gap existing between the coupling flanges or between two successive conveying pipes are specified in dependence on the respective inner diameter of the conveying pipes. In this connection, the radial extension of the coupling flanges is also prescribed, so that coupling rings of one manufacturer can be coupled without problems to conveying pipes of different manufacturers.
Moreover, it is indisputable that when using conveying pipes for hydraulically transporting solids that the wear at the inlet end of a conveying pipe is greater than in the area following in the conveying direction. As a result of this wear, the inner end of the conveying pipe on the inlet side widens more and more in a conical or trumpet-like shape and travels on in the conveying direction until the wall thickness between the inner conical portion and the transition from the inner end face of the coupling flange and the adjacent outer surface of the conveying pipe becomes so thin that there is the danger that the coupling flange tears off. However, the pipe portion is still fully useful over the greatest portion of its length. Nevertheless, the conveying pipe has to be completely replaced.